Two days into their opening arguments, House Republican prosecutors in President Clinton's impeachment trial seem close to achieving one of their major tactical goals: convincing Senate Republicans that they should call witnesses to buttress their case.

Although the plan could rekindle partisan warfare, several influential GOP senators who had been uneasy about calling witnesses now say they were persuaded by the House managers this week that witnesses must be called to resolve crucial contradictory testimony by the president, Monica S. Lewinsky and others who were involved in the White House sex scandal.

Senators were more leery of the notion of inviting the president to testify, a plan House managers have pressed in recent days -- and that the White House has rejected. "I see no value in having the president come," said Sen. Robert F. Bennett (R-Utah), "because I'm confident if he did come he would simply repeat the same sort of tortured evasions he made before and then claim they are accurate statements."

Still, Bennett said in an interview: "If you had taken a straw poll a week to 10 days ago, there probably would not have been enough votes for witnesses. . . . My sense of things now is that there are."

"The argument for witnesses is strengthening" and "unless the president's lawyers next week stipulate to the facts we may have to move towards live witnesses," added Sen. Mitch McConnell (Ky.).

Other GOP senators who say they can support calling witnesses include Ted Stevens (Alaska), and three New England moderates whom the White House had hoped might support its position that testimony is not necessary.

Provided this trend holds up throughout the White House lawyer's counter-arguments next week, Senate Republicans are likely to prevail on a vote to allow testimony from such figures as Lewinsky, the ex-White House intern; Betty Currie, the president's personal secretary; and Vernon Jordan, a presidential confidant. Prosecutors have until Jan. 25 to submit a witness list.

Under Senate rules and the trial procedures adopted last week, it would take a simple majority of the Senate -- or 51 votes if all senators are present -- to call witnesses, who would have to be voted on individually. With Republicans controlling the Senate by a margin of 55 to 45, this means even if all Democrats vote against witnesses, they would still have to pick up at least six Republican votes to keep witnesses from being called.

While the Senate trial so far has been marked by unusual comity between the parties, the Republicans' mounting insistence on witnesses over strong Democratic objections could trigger the kind of furious partisan struggle that rocked the House last year.

The introduction of witnesses could also prolong the trial, a fact that opponents are likely to seize upon in arguing against it. Witnesses summoned by the Senate would have to be deposed by the House managers and the White House lawyers in advance of their possible testimony on the Senate floor.

White House officials have warned that if the prosecutors insist on presenting witnesses -- something Republicans in the House declined to do during their impeachment deliberations -- then Clinton's lawyers would insist on calling other witnesses who might cast a more favorable light on the president.

Until now, many senators have assumed that with the parties so divided over impeachment that it would be impossible to muster the two-thirds majority that would be necessary to convict the president. However, White House officials are wary that calling witnesses could open Pandora's Box to additional new damaging evidence that could change the course of a trial.

Sen Max Baucus (D-Mont.) complained yesterday that the push for witnesses "has a partisan flavor" and said the Senate was drifting toward a clash between Democrats and Republicans. Sen. Byron L. Dorgan (D-N.D.) acknowledged a hardening of party lines around the issue.

"It now appears almost certain there will be witnesses," said Dorgan, a member of the Senate Democratic leadership. "The spectacle of calling Monica Lewinsky to the Senate well . . . will create a carnival-like atmosphere."

A team of House Republican prosecutors opened the impeachment trial Thursday with a series of hard-hitting presentations in which they methodically laid out what they called Clinton's "multifaceted scheme to obstruct justice" to cover up his affair with Lewinsky.

Using charts, graphics and detailed chronologies, the managers argued that the president spun a web of deceit and lied repeatedly in sworn testimony about the extent of his sexual relationship with Lewinsky. Yesterday, the prosecutors urged the Senate to call Lewinsky, Jordan and others to testify to reconcile conflicts between theirs and the president's previous testimony.

Many GOP senators, including three New England moderates, praised House managers for effectively marshaling the evidence and highlighting contradictory testimony. .

Sen. Susan M. Collins (R-Maine) said the managers strengthened her resolve to call witnesses. "I'm inclined to believe that we do need witnesses to resolve the contradictory testimony that's been given before the grand jury by various witnesses," Collins said.

Sen. James M. Jeffords (R-Vt.), another moderate who has seemed to waver on the subject, said yesterday that "there might be a half-dozen witnesses I might consider calling." Sen. John H. Chafee (R-R.I.), also favors calling witnesses. A fourth New England moderate, Sen. Olympia J. Snowe (R-Maine), says she is undecided.

Stevens, the Alaskan Republican who had earlier expressed reservations about hearing live testimony, said he was now "convinced" Lewinsky and Currie must take the stand to discuss how Lewinsky transferred the president's gifts to Currie.

"There is an absolute conflict there," Stevens said.

Republicans were more ambivalent about calling the president to testify, though some talked of issuing a nonbinding request. "There is a difference between inviting him and subpoenaing him. An invitation could be offered," said Sen. Connie Mack (R-Fla.).

Senate Majority Leader Trent Lott (R-Miss.) left the decision to Clinton, saying, "That's up to him."

While Republicans appeared torn, Democrats were more uniform in rejecting the idea of calling Clinton. Minority Leader Thomas A. Daschle (D-S.D.) called it a "nonissue" because the White House has indicated that Clinton will not appear and maintained the Senate lacks the power to force him to.

"This country has 200 years of history where a person doesn't have to prove his innocence in court," added Sen. Patrick J. Leahy (D-Vt.). "It would send a terrible, terrible signal to the rest of the world if after 220 years we would be changing something that is the bedrock of our society."

For the most part, Democrats have dismissed much of the House presentation as the repackaging of well-worn allegations and argue that there is adequate evidence and testimony in the House impeachment record from which to make a judgment. "The House Republican managers were well prepared . . . but I know as a trial lawyer that an opening statement doesn't make a trial," said Sen. Richard J. Durbin (R-Ill.)

Some Republicans, as well as Democrats, cautioned that the issue of calling witnesses was likely to remain up in the air until after White House lawyers presented Clinton's case, and it becomes clear whether discrepancies could be narrowed by stipulating to facts or questioning witnesses by deposition.

"I think it's important for all of us to make our decision based on the totality of the presentations by both the House managers and the White House. So I'm not prepared . . . to say witnesses are necessary," said Snowe.

Sen. Jon Kyl (R-Ariz.) raised a different point. "Until you see what the White House strategy is, I don't see how you could have an opinion" on whether to call witnesses. If the White House decides to make its case on law rather than fact, witnesses would not be needed, Kyl said.

Rep. Robert L. Barr Jr. (R-Ga.), one of the House Judiciary Committee prosecutors, said "I sense that our arguments are getting through to the senators."

"You never know, but they all seem to be listening very intently to what's going on," he added. "A lot of them taking notes, and that's always a good sign."